Add Phase 1 D3D12 tests for Device and Fence

- Implement real D3D12 tests for Device (feature level, descriptor handle,
  shader model, resource binding tier, tiled resources)
- Implement real D3D12 tests for Fence (create, signal, wait, event)
- Move tests from tests/D3D12_engine/test/ to tests/RHI/D3D12/
- All 22 tests pass

tests/RHI/D3D12/fixtures/D3D12TestFixture.cpp

@@ -0,0 +1,77 @@
+#include "D3D12TestFixture.h"
+
+ComPtr<ID3D12Device> D3D12TestFixture::mDevice;
+
+void D3D12TestFixture::SetUpTestSuite() {
+    HRESULT hr = D3D12CreateDevice(
+        nullptr,
+        D3D_FEATURE_LEVEL_12_0,
+        IID_PPV_ARGS(&mDevice)
+    );
+    
+    if (FAILED(hr)) {
+        GTEST_SKIP() << "Failed to create D3D12 device";
+        return;
+    }
+}
+
+void D3D12TestFixture::TearDownTestSuite() {
+    mDevice.Reset();
+}
+
+void D3D12TestFixture::SetUp() {
+    if (!mDevice) {
+        GTEST_SKIP() << "D3D12 device not available";
+        return;
+    }
+    
+    D3D12_COMMAND_QUEUE_DESC queueDesc = {};
+    queueDesc.Type = D3D12_COMMAND_LIST_TYPE_DIRECT;
+    
+    HRESULT hr = mDevice->CreateCommandQueue(&queueDesc, IID_PPV_ARGS(&mCommandQueue));
+    if (FAILED(hr)) {
+        GTEST_SKIP() << "Failed to create command queue";
+        return;
+    }
+    
+    hr = mDevice->CreateCommandAllocator(D3D12_COMMAND_LIST_TYPE_DIRECT, IID_PPV_ARGS(&mCommandAllocator));
+    if (FAILED(hr)) {
+        GTEST_SKIP() << "Failed to create command allocator";
+        return;
+    }
+    
+    hr = mDevice->CreateCommandList(0, D3D12_COMMAND_LIST_TYPE_DIRECT, mCommandAllocator.Get(), nullptr, IID_PPV_ARGS(&mCommandList));
+    if (FAILED(hr)) {
+        GTEST_SKIP() << "Failed to create command list";
+        return;
+    }
+}
+
+void D3D12TestFixture::TearDown() {
+    if (mCommandQueue) {
+        WaitForGPU();
+    }
+    mCommandList.Reset();
+    mCommandAllocator.Reset();
+    mCommandQueue.Reset();
+}
+
+void D3D12TestFixture::WaitForGPU() {
+    if (!mCommandQueue || !mDevice) return;
+    
+    ComPtr<ID3D12Fence> fence;
+    UINT64 fenceValue = 1;
+    
+    HRESULT hr = mDevice->CreateFence(0, D3D12_FENCE_FLAG_NONE, IID_PPV_ARGS(&fence));
+    if (SUCCEEDED(hr)) {
+        mCommandQueue->Signal(fence.Get(), fenceValue);
+        if (fence->GetCompletedValue() < fenceValue) {
+            HANDLE eventHandle = CreateEvent(nullptr, FALSE, FALSE, nullptr);
+            if (eventHandle) {
+                fence->SetEventOnCompletion(fenceValue, eventHandle);
+                WaitForSingleObject(eventHandle, INFINITE);
+                CloseHandle(eventHandle);
+            }
+        }
+    }
+}